In a vehicle, a prime mover drives a set of wheels, or other ground engaging traction devices, which engages a support surface, such as a road or ground, to move the vehicle. Because the output of the prime mover, which includes engines and/or motors, must adapt to different speed requirements and road conditions, a transmission is located between the prime mover and a set of wheels to adjust the output of the prime mover in order to move the vehicle at different speeds. The transmission includes an input shaft, operatively connected to an output shaft of the prime mover, and an output shaft, operatively connected to a drivetrain connected to the wheels. Transmissions, however, are not limited to applications involving powered vehicles, but are also used in human propelled vehicles, such as a bicycle, and in industrial machinery used in factories as well as in field operations, for instance at oil drilling operations.
The transmission is a system configured to transmit power and torque from the prime mover to the drive train. In one type of conventional transmission, the transmission includes a variety of gears, shafts, and clutches configured to transmit torque through the transmission at finite, stepped gear ratios. In another type of transmission, a continuously variable transmission (CVT) is configured to continuously vary the ratio of an input rotational speed to an output rotational speed under control of a vehicle operator, typically by a speed controller input such as provided by accelerator.
“On road” vehicles having transmissions include transportation vehicles, such as passenger vehicles and buses, and work vehicles, such as semi-tractors and vehicles used to plow snow, spread salt, or carry refuse. Additionally “off-road” vehicles having transmissions include agricultural vehicles, construction vehicles, such as graders and plows, and lawn maintenance vehicles. Agricultural vehicles can also include a power take off (PTO) driven by the transmission. Likewise, stationary work machines can include transmissions. Such stationary work machines include machines for providing power, such as generators or wind machines, machines used in the oil industry to drill for or to deliver oil, and machines used in the timber industry used to cut or process timber.
In one type of CVT, a plurality of planets is disposed between an input disc and an output disc to vary the ratio of an input speed of the input disc to an output speed of the output disc. Each of the planets is supported for rotation about a central axis, wherein the angle of the central axis is configured to be adjustable to thereby vary the ratio of the input speed to the output speed. The rotary input disc and the rotary output disc are configured to steplessly or continuously vary the ratio of the input speed to the output speed in response to the orientation of the planets. The input disc includes external gear teeth configured to engage the drive shaft or an intermediate shaft coupled to the drive shaft. The output disc includes external gear teeth that are in mesh with and drive shaft or a corresponding gear of the drive train.
Continuously variable transmissions are known to include a large number of components arranged in complex configurations. Because the cost of a CVT can be expensive due to the large number of components, it is desirable to reduce the number of components to reduce the overall cost. In addition, by reducing the number of components, repair costs can be reduced. Likewise, the number of component failures can also be reduced including those resulting from the incorrect assembly of components. What is needed, therefore, is a CVT having an improved manufacturability, improved reliability, and reduced cost.